TY - JOUR
A1 - Sarma, Dominik
A1 - Gawlitza, Kornelia
A1 - Rurack, Knut
T1 - Polystyrene Core−Silica Shell Particles with Defined Nanoarchitectures as a Versatile Platform for Suspension Array Technology
JF - Langmuir
N2 - The need for rapid and high-throughput screening in analytical laboratories has led to significant growth in interest in suspension array technologies (SATs), especially with regard to cytometric assays targeting a low to medium number of analytes. Such SAT or bead-based assays rely on spherical objects that constitute the analytical platform. Usually, functionalized polymer or silica (SiO2) microbeads are used which each have distinct advantages and drawbacks. In this paper, we present a straightforward synthetic route to highly monodisperse SiO2-coated polystyrene core−shell (CS) beads for SAT with controllable architectures from smooth to raspberry- and multilayer-like shells by varying the molecular weight of poly(vinylpyrrolidone) (PVP), which was used as the stabilizer of the cores. The combination of both organic polymer core and a structurally controlled inorganic SiO2 shell in one hybrid particle holds great promises for flexible next-generation design of the spherical platform. The particles were characterized by electron microscopy (SEM, T-SEM, and TEM), thermogravimetry, flow cytometry, and nitrogen adsorption/desorption, offering comprehensive information on the composition, size, structure, and surface area. All particles show ideal cytometric detection patterns and facile handling due to the hybrid structure. The beads are endowed with straightforward modification possibilities through the defined SiO2 shells. We successfully implemented the particles in fluorometric SAT model assays, illustrating the benefits of tailored surface area which is readily available for small-molecule anchoring. Very promising assay performance was shown for DNA hybridization assays with quantification limits down to 8 fmol.
KW - core-shell particles
KW - shell morphology
KW - flow cytometry
KW - scanning electron microscopy
KW - stabilizer
Y1 - 2016
UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000374706700018
U6 - http://dx.doi.org/DOI: 10.1021/acs.langmuir.6b00373
SN - 0743-7463
VL - 32
IS - 15
SP - 3717
EP - 3727
PB - American Chemical Society
CY - Washington, DC, USA
ER -
TY - GEN
A1 - Tiebe, Carlo
A1 - Gawlitza, Kornelia
T1 - Gas standards for the calibration of novel fluorescence sensors for ammonia
N2 - Ammonia and its conversion product ammonium have a strong negative impact on human health and ecosystems. Most ammonia measurements in ambient air are performed in the molar fraction range (0.5 to 500) nmol/mol. There is a need for reliable traceable ammonia gas standards as well as in situ analytical procedures for the monitoring of ammonia in ambient air.
The permeation method is an effective tool for dynamically generating precise gas standards with a low uncertainty in the concentration range of a few nmol/mol to several µmol/mol in an inert carrier gas, e. g. pure nitrogen or purified ambient air. Here, we present our ammonia gas standard generator as well as results of the characterisation of its individual components supporting the uncertainty assessment according to GUM for stable gas concentrations in this range.
In order to detect ammonia in the nmol/mol-range, a suitable sensor has to be developed. In this contribution, we therefore additionally present first approaches on the development of such a sensor using optical fluorescence as transduction mechanism due to its intrinsically high sensitivity and high spatial resolution. Incorporation of a fluorescent dye, which shows fluorescence enhancement in the presence of ammonia, into a polymer matrix allows to reversibly recognize low amounts of ammonia. It can be concluded that fluorescence sensor is a robust tool for measurements of ammonia; however it needs calibration for the planed use.
KW - Ammonia
KW - Fluorescence sensor
KW - Permeation
KW - Test gas generation
Y1 - 2016
ER -
TY - JOUR
A1 - Climent, Estela
A1 - Biyikal, Mustafa
A1 - Gawlitza, Kornelia
A1 - Dropa, T.
A1 - Urban, M.
A1 - Costero, A. M.
A1 - Martínez-Máñez, R.
A1 - Rurack, Knut
T1 - A rapid and sensitive strip-based quick test for nerve agents Tabun, Sarin, and Soman using BODIPY-modified silica materials
JF - Chemistry - a European journal
N2 - Test strips that in combination with a portable fluorescence reader or digital camera can rapidly and selectively detect chemical warfare agents (CWAs) such as Tabun (GA), Sarin (GB), and Soman (GD) and their simulants in the gas phase have been developed. The strips contain spots of a hybrid indicator material consisting of a fluorescent BODIPY indicator covalently anchored into the channels of mesoporous SBA silica microparticles. The fluorescence quenching response allows the sensitive detection of CWAs in the μg m−3 range in a few seconds.
KW - Chemical warfare agents
KW - Fluorescence
KW - Hybrid sensor materials
KW - Nerve gases
KW - Test strip analysis
Y1 - 2016
U6 - http://dx.doi.org/10.1002/chem.201601269
SN - 0947-6539
SN - 1521-3765
VL - 22
IS - 32
SP - 11138
EP - 11142
PB - Wiley
CY - Online Library
ER -
TY - GEN
A1 - Gawlitza, Kornelia
T1 - Integrating fluorescent molecularly imprinted polymer (MIP) sensor particles with a microfluidic platform for nanomolar small-molecule detection in water
N2 - Besides the traditional areas of application such as separation and enrichment which made molecularly imprinted polymers (MIPs) very attractive, they have emerged as a valuable detection tool in the field of environmental analysis due to the low production costs, high stability, format adaptability and the possibility to imprint and thus specifically recognize a wide variety of target analytes. Regarding optical sensing, however, MIPs have only been used in considerably few applications, especially in fluorescence sensors, basically because of the challenge to incorporate a fluorescently responding moiety into a polymer matrix. One way to overcome this limitation is the coating of a thin MIP layer onto the surface of silica nanoparticles using tailor-made fluorescent indicator monomers or cross-linkers for direct transfer of the binding event into an optical signal.
Regarding sensors for environmental monitoring, microfluidic devices utilizing optical detection modules are especially appealing because of their versatility in terms of miniaturization and automation. So far, MIPs have only rarely been used in combination with microfluidic sensor devices.
Here, we present the hydrogen bond-mediated optical response of fluorescent MIP sensor particles against a typical small-molecule analyte 2,4-D (2,4-dichlorophen¬oxyacetic acid) which is an important herbicide widely used in agriculture and known to cause adverse health effects when ingested by contaminated water. By combining the sensor particles with droplet-based 3D microfluidics, a microfluidic phase-transfer assay was designed which enables the direct analysis of 2,4-D in river and lake water without sample pre-treatment or clean-up.
KW - MIPs
KW - Fluorescence
KW - Sensor
KW - Water-monitoring
Y1 - 2017
ER -
TY - CHAP
A1 - Gawlitza, Kornelia
A1 - Wan, Wei
A1 - Wagner, Sabine
A1 - Rurack, Knut
ED - Tiwari, Ashutosh
ED - Uzun, Lokman
T1 - Fluorescent Molecularly Imprinted Polymers
T2 - Advanced Molecularly Imprinting Materials
N2 - An ideal sensor system is a combination of a selective receptor, an effective transducer, and a sensitive detector. To utilize molecularly imprinted polymers (MIPs) as responsive recognition phases in sensors, the employment of fluorescent molecules or nanoparticles (NPs) that show prominent changes in their spectroscopic properties after binding of the target molecule in the MIP’s cavity is particularly attractive. Such fluorescent MIPs (fMIPs) act through target-induced quenching, enhancement, or spectral shifts of the fluorescence. This contribution introduces different strategies of incorporation of fluorescent dyes, probes, and NPs into fMIPs. In addition, various sensing mechanisms are reviewed, and depending on the application of the sensor, the different deployable formats, their advantages, drawbacks, and impact will be presented and discussed.
KW - Dyes
KW - Fluorescence
KW - Molecular imprinted polymers
KW - Quantum dots
KW - Sensors
Y1 - 2017
SN - 978-1-119-33629-7
SP - 89
EP - 128
PB - Scrivener Publishing, WILEY
CY - Beverly, MA
ET - 1
ER -
TY - JOUR
A1 - Climent, Estela
A1 - Biyikal, Mustafa
A1 - Gawlitza, Kornelia
A1 - Dropa, T.
A1 - Urban, M.
A1 - Costero, A. M.
A1 - Martínez-Máñez, R.
A1 - Rurack, Knut
T1 - Determination of the chemical warfare agents Sarin, Soman and Tabun in natural waters employing fluorescent hybrid silica materials
JF - Sensors and Actuators B: Chemical
N2 - A novel mesoporous silica material containing boron–dipyrromethene (BODIPY) moieties (I) is employed for the detection of nerve agent simulants (NASs) and the organophosphate nerve or chemical warfare agents (CWAs) Sarin (GB), Soman (GD), and Tabun (GA) in aqueous environments. The reactive BODIPY dye with an optimum positioned hydroxyl group undergoes acylation reactions with phosph(on)ate substrates, yielding a bicyclic ring. Due to aggregation of the dyes in water, the sensitivity of the free dye in solution is very low. Only after immobilization of the BODIPY moieties into the silica substrates is aggregation inhibited and a sensitive determination of the NASs diethyl cyanophosphonate (DCNP), diethyl chlorophosphate (DCP) and diisopropyl fluorophosphate (DFP) possible. The signaling mode is a strong quenching of the fluorescence, reaching LODs in the pM range. The best performing hybrid material was singled out from a library of hybrid silicas varying in morphology and surface functionalization. The response to actual CWAs such as GB, GD, and GA has also been tested, offering similar behavior as for the simulants. The proposed reaction mechanism has been verified by investigation of other model materials, containing for instance BODIPY moieties without an optimum hydroxyl group (III) or a BODIPY dye with an all-aliphatic counterpart (IV). The latter can only form a monocyclic reaction product, showing much less reactivity as I. Assays with other possible competitors have been additionally carried out, showing favorably low cross-reactivities. Finally, the determination of NASs in several natural waters has been demonstrated.
KW - Nerve agent simulants
KW - Mesoporous silica materials
KW - Fluorescence detection
Y1 - 2017
UR - http://www.sciencedirect.com/science/article/pii/S0925400517303428
UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS&DestLinkType=FullRecord;UT=WOS:000400803700129
U6 - http://dx.doi.org/10.1016/j.snb.2017.02.115
SN - 0925-4005
VL - 246
SP - 1056
EP - 1065
PB - Elsevier B.V.
ER -
TY - JOUR
A1 - Ritter, B.
A1 - Haida, P.
A1 - Fink, F.
A1 - Krahl, T.
A1 - Gawlitza, Kornelia
A1 - Rurack, Knut
A1 - Scholz, G.
A1 - Kemnitz, E.
T1 - Novel and easy access to highly luminescent Eu and Tb doped ultra-small CaF2, SrF2 and BaF2 nanoparticles – structure and luminescence
JF - Dalton Transactions
N2 - A universal fast and easy access at room temperature to transparent sols of nanoscopic Eu3+ and Tb3+ doped CaF2, SrF2 and BaF2 particles via the fluorolytic sol–gel synthesis route is presented. Monodisperse quasi-spherical nanoparticles with sizes of 3–20 nm are obtained with up to 40% rare earth doping showing red or green luminescence. In the beginning luminescence quenching effects are only observed for the highest content, which demonstrates the unique and outstanding properties of these materials. From CaF2:Eu10 via SrF2:Eu10 to BaF2:Eu10 a steady increase of the luminescence intensity and lifetime occurs by a factor of ≈2; the photoluminescence quantum yield increases by 29 to 35% due to the lower phonon energy of the matrix. The fast formation process of the particles within fractions of seconds is clearly visualized by exploiting appropriate luminescence processes during the synthesis. Multiply doped particles are also available by this method. Fine tuning of the luminescence properties is achieved by variation of the Ca-to-Sr ratio. Co-doping with Ce3+ and Tb3+ results in a huge increase (>50 times) of the green luminescence intensity due to energy transfer Ce3+ → Tb3+. In this case, the luminescence intensity is higher for CaF2 than for SrF2, due to a lower spatial distance of the rare earth ions.
KW - Luminescence materials
KW - Alkaline earth metal fluorides
KW - Fluorolytic sol–gel synthesis
Y1 - 2017
UR - http://apps.webofknowledge.com/full_record.do?product=WOS&search_mode=GeneralSearch&qid=51&SID=T2YZLlD6VdrLIKERSvM&page=1&doc=1
U6 - http://dx.doi.org/10.1039/C6DT04711D
VL - 46
IS - 9
SP - 2925
EP - 2936
PB - Royal Society of Chemistry
ER -
TY - GEN
A1 - Bartelmeß, Jürgen
A1 - Gawlitza, Kornelia
A1 - Bartholmai, Matthias
A1 - Rurack, Knut
T1 - Developments towards the fluorescence based sensing of hazardous gases
N2 - Fluorescence based sensing is a versatile approach for the trace analysis outside of the laboratory, requiring suitable sensor materials and their integration into sensing devices. The versatility of fluorophores as probes, especially in terms of the possibility to tailor their optical as well as their recognition properties by synthetic modifications in a wide range, renders them a superior active component for the preparation of optical sensor devices. Recent works at BAM in this field include, for example, the detection of nerve gas agents, illustrating impressively the aforementioned benefits of fluorophores in optical sensing applications.
In the interdisciplinary approach presented here, we target hazardous gases such as ammonia, benzene, and hydrogen sulfide, next to others, which pose a major threat to human health and environmental safety and for which the availability of a sensitive and reliable detection method is highly desirable.
The dyes presented follow a “turn-on” fluorescence schematic which allows for the selective and sensitive detection of the respective gaseous analyte. The immobilization of the probe in polymeric matrices is then the next step toward the fabrication of a prototype device for molecular sensing.
KW - Gas sensing
KW - Fluorescence
KW - KonSens
Y1 - 2017
ER -
TY - GEN
A1 - Tiebe, Carlo
A1 - Banach, Ulrich
A1 - Hübert, Thomas
A1 - Gawlitza, Kornelia
A1 - Bartholmai, Matthias
T1 - Development of a gas standard generator
N2 - Pollution through emission of toxic gases is an increasing problem for the environment. It affects similarly agricultural, industrial and urban areas. In future, environmental emissions in ambient air must be monitored at even lower concentrations as nowadays. One environmental relevant compound is ammonia and its conversion product ammonium that have strong negative impact on human health and ecosystems. Most ammonia measurements in ambient air are performed in the range below 1000 nmol·mol-1 and thus there is a need for reliable traceable ammonia gas standards and in addition in situ analytical procedures for monitoring (in ambient air to avoid that thresholds are exceeded). Therefore, the use of reference materials is necessary for development accompanying test or for calibration, e. g. of structure-integrated sensors and mobile multi-gas sensors.
The developed gas standard generator produces gas mixtures that comply with the metrological traceability for ammonia gas standards in the desired environmentally relevant measurement range. The method is based on the permeation of ammonia through a membrane at constant temperature and pressure. The resulting ammonia penetrant gas flow is then mixed with a carrier gas flow to generate a gas standard flow of known concentration. The dynamic rage is enlarged by using a two dilution steps. Depending on the permeation rate, generable molar fractions are possible in the range nmol·mol-1 to a few µmol·mol-1. We present the design of an ammonia gas standard generator and first results of the characterisation of its individual components supporting the uncertainty assessment according to GUM for stable gas concentrations in this range. The relative uncertainty of the generated ammonia gas standard is smaller than 4 % (k = 2).
KW - Gas standard generator
KW - Permeation method
KW - Ammonia
Y1 - 2017
ER -
TY - GEN
A1 - Neumann, Patrick P.
A1 - Johann, Sergej
A1 - Tiebe, Carlo
A1 - Gawlitza, Kornelia
A1 - Bartelmeß, Jürgen
A1 - Bartholmai, Matthias
T1 - Airborne Remote Gas Sensing and Mapping
N2 - Leaking methane (CH4) from infrastructures, such as pipelines and landfills, is critical for the environment but can also pose a safety risk. To enable a fast detection and localization of these kind of leaks, we developed a novel robotic platform for aerial remote gas sensing. Spectroscopic measurement methods for remote sensing of selected gases lend themselves for use on mini-copters, which offer a number of advantages for inspection and surveillance over traditional methods. No direct contact with the target gas is needed and thus the influence of the aerial platform on the measured gas plume can be kept to a minimum. This allows to overcome one of the major issues with gas-sensitive mini-copters. On the other hand, remote gas sensors, most prominently Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensors have been too bulky given the payload and energy restrictions of mini-copters. Here, we present the Unmanned Aerial Vehicle for Remote Gas Sensing (UAV-REGAS), which combines a novel lightweight TDLAS sensor with a 3-axis aerial stabilization gimbal for aiming on a versatile hexacopter. The proposed system can be deployed in scenarios that cannot be addressed by currently available robots and thus constitutes a significant step forward for the field of Mobile Robot Olfaction (MRO). It enables tomographic reconstruction of gas plumes and a localization of gas sources. We also present first results showing its performance under realistic conditions.
KW - Tunable Diode Laser Absorption Spectroscopy (TDLAS)
KW - UAV-REGAS
KW - Mobile Robot Olfaction
KW - Tomographic reconstruction of gas plumes
KW - Localization of gas sources
Y1 - 2017
ER -